<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    function foo() {
        var a = 1
        var b = 2
        {
            let b = 3
            var c = 4
            let d = 5
            console.log('a,b:', a, b)
        }
        console.log('b,c,d:', b, c, d)
    }
</script>
</body>
</html>